Educational integration of children with migration background is an important issue in the social sciences. Few studies exist that quantify the disadvantage of immigrant children in education and there has not been any attempt to identify institutional conditions of the education system that contribute to educational integration. Using data from five international student assessments, this study tries to fill that gap. First, Blinder-Oaxaca decompositions are used to allow for a comparison of (dis)integration of students with migration background across countries and time. In a second step, (dis)integration is related to institutional characteristics of the schooling system. The study shows that early education, time in school and central exams furthers integration, while social segregation of students among schools is detrimental to educational integration.